Our MDO (Modular Down Outer) is an extremely unique design. It is manufactured from 94% polyester and 6% spandex which not only creates a dynamic stretch for comfort but is also highly durable for active outdoor pursuits. Its external shell fabric is a 3-layer fabric with a membrane sandwiched between the outer shell and the inner tricot finish. The membrane is designed and manufactured by Schoeller and is called C change.